In April, Miriam Garay had her four children baptized by the Rev. Morgan Kuhl at St. Mary of the Assumption Roman Catholic Church on the north shore of Staten Island. Yesterday, she was there again, stunned to learn that the priest who had blessed her family's entrance into Catholicism had been arrested, accused of trying to have a sexual liaison with a teen-age boy.

''Now my 10-year-old son is asking me a lot of questions,'' Ms. Garay said after attending Mass. ''He doesn't want to come to catechism class. He wants to know if Father Morgan did something bad, and I just don't know what to tell him. I'll try to find answers, but I don't know.''

In fact, the worshipers who came to the 146-year-old church in Port Richmond yesterday seemed at a loss to explain how their priest had come to be arrested on Tuesday in a park in Perth Amboy, N.J. The authorities said he had been expecting to meet an on-line correspondent he had assumed was a 15-year-old boy, but who was really an undercover F.B.I. agent.

According to the Federal Bureau of Investigation, agents had been communicating with Father Kuhl on the Internet since April, pretending to be teen-age boys, and he had tried to set up meetings with them.

After Father Kuhl was arrested in Washington Park in Perth Amboy, agents found four unopened packages of condoms in his car, The Associated Press reported. The agents also found a printout of an E-mail message one of them had sent confirming plans to meet at the bleachers in the park, according to the A.P.

Father Kuhl was charged with interstate travel to have sex with a minor, which carries a sentence of up to 10 years in prison. He was arraigned in United States District Court in Trenton, where Magistrate John J. Hughes released him on a $50,000 bond and ordered him confined to the church's rectory.

Father Kuhl, 32, was the administrative priest at St. Mary's and was said to be under serious consideration for the post of pastor, or leader of the parish. Ordained in 1993, he came to St. Mary's in November from Holy Child Church in the Annandale section of Staten Island, where he was a parochial vicar, or assistant priest.

''The fact he was named an administrator only five years after ordination shows tremendous confidence in him,'' said Joseph Zwilling, a spokesman for the Roman Catholic Archdiocese of New York. ''Somewhere down the road, he would have been considered for pastor.''

Though he was relatively new at St. Mary's, a congregation of about 500 people, many of them Mexican, Father Kuhl had already earned much respect and affection, parishioners said. He did not officiate at the Spanish-language services because his knowledge of the language was limited, but he went to Mexico in the summer to try to master it.

''He's a fine young man, a fine young man,'' Matteo Lumetta said as he waited for the English-language Mass to begin. ''I couldn't believe it.''

Mr. Lumetta, 72, has attended services at St. Mary's for 50 years and sent his four children to its school, which is now closed. ''Something like this brings people out,'' he added. ''It unites a parish.''

Luis Soto, 15, said he had never noticed anything unusual about the priest's behavior.

''He was nice, but there was never any suggestion of anything else,'' he said ''I shared my thoughts with him. I confessed to him.''

The shock expressed yesterday was not confined to the laity.

The Rev. Mark Oguamanam, a visiting priest from Nigeria, arrived just as the news about Father Kuhl was spreading. ''It was a big shock, he said. ''What affects one priest affects all of us.''

Msgr. Edward O'Donnell, vice chancellor for priest personnel at the New York Archdiocese, addressed the congregation yesterday. He tried to calm an elderly woman who told him in a quivering voice: ''I feel as if I've lost someone. I feel like a waif.''

Speaking in English and Spanish, the monsignor asked anyone who wanted to discuss Father Kuhl or offer information to call him at the chancellery in Manhattan.

''We are deeply pained by the devastating report,'' he said. ''Prior to this, there was not a hint that Father Morgan might have a problem. We are taking steps to give him the psychological and legal help he needs, but we also want to address the pain and hurt in the parish.''

The Rev. William Harder, who served in Father Kuhl's post several years ago, returned Friday to take over administration of the church.

Asked what steps he thought necessary to help the church heal, he said, ''It's a mystery to me how it will take place, but I trust it will.''